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Re: Optional parameters [message #38192 is a reply to message #38191]

Tue, 24 February 2004 12:13

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Tue, 24 Feb 2004 10:59:29 -0700, Pavel Romashkin wrote:

> I agree. I never had a problem with this because I never put unneeded
> variables in a call to a procedure. I fail to see the logic in putting
>
> myfunction, var1=uselessvar
>
> as opposed to just
>
> myfunction
>
> and then worrying about uselessvar getting defined all of a sudden. The
> only time this might happen in real life I suppose is if you use
> copy-paste to insert function calls that address all of the provided keywords.

I'd offer another real life example where read-write keyword variables
can get you into trouble. When you call a function several times in a
row, expecting the same results each time, but in actuality the
keyword variable is defined after the first invocation, which can
change the function's behavior:

a=myfunc(test,FUNNY_VARIABLE=foo) ; foo undefined
a=myfunc(test,FUNNY_VARIABLE=foo) ; foo defined
a=myfunc(test,FUNNY_VARIABLE=foo) ; foo defined

For this reason, I try to make keywords either exclusively read
(i.e. pass in a value), or exclusively write (i.e. return a value),
and not both. It is rather convenient, though, to append a keyword
for the sole purpose of keeping some expensive-to-compute data around
between calls to the function: this is usually where I get tripped up.

JD

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[Message index]

		Re: Optional parameters By: Pavel Romashkin on Wed, 25 February 2004 10:21
		Re: Optional parameters By: David Fanning on Wed, 25 February 2004 09:26
		Re: Optional parameters By: Craig Markwardt on Wed, 25 February 2004 08:48
		Re: Optional parameters By: David Fanning on Wed, 25 February 2004 07:08
		Re: Optional parameters By: Paul Van Delst[1] on Wed, 25 February 2004 06:49
		Re: Optional parameters By: Craig Markwardt on Tue, 24 February 2004 21:50
		Re: Optional parameters By: JD Smith on Tue, 24 February 2004 14:03
		Re: Optional parameters By: R.G. Stockwell on Tue, 24 February 2004 14:02
		Re: Optional parameters By: Pavel Romashkin on Tue, 24 February 2004 13:45
		Re: Optional parameters By: JD Smith on Tue, 24 February 2004 12:13
		Re: Optional parameters By: Pavel Romashkin on Tue, 24 February 2004 09:59
		Re: Optional parameters By: David Fanning on Tue, 24 February 2004 09:08
		Re: Optional parameters By: David Fanning on Tue, 24 February 2004 08:31
		Re: Optional parameters By: JD Smith on Tue, 24 February 2004 08:10
		Re: Optional parameters By: David Fanning on Mon, 23 February 2004 17:39
		Re: Optional parameters By: David Fanning on Mon, 23 February 2004 17:05

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